Empty seas coming to a shore near you

12072012

Last week I had the pleasure of entertaining some old friends and colleagues for a writing workshop in Adelaide (don’t worry – they all came from southern Australia locations, so no massive carbon footprints for overseas travel). I’m happy to report it was a productive (and epicurean) week, but that’s not really the point of today’s post.

The left-hand maps are the catch rates of sharks in the Java Sea (north of Java, Indonesia), and the right-hand images are catch rates of rays. The top panels represent data collected during cruises done in 1976, and the bottom maps show the same area in 1997.

Take a good, close look – anything jump out? Unless you’re officially blind, you’ll notice the stunning reduction in shark and ray abundance over the 20-year period (it works out to be about a 90 % reduction in biomass). No, ‘stunning’ isn’t strong enough – ‘catastrophic’ is more à propos. Personally, I uttered something more like “holy f&%k!” when I first saw these figures.

CB readers might recall another paper also published in 2009 (of which Rik was a co-author) where we examined shark declines in fished and unfished reefs in Australia’s northern Exclusive Economic Zone – we found evidence for shark declines then, and predicted that the continued penetration of illegal fisheries into waters to our north would eventually wipe out Australian shark & ray populations. We called this phenomenon the “protein mining wave”.

In summary, we can probably expect northern Australia’s shark and ray populations to look a lot like the above figures if we don’t get a serious handle on illegal fishing in our EEZ. Some might say that’s an impossible task. For the sake of our marine biodiversity, I hope not.